Hey all, just ordered a Lymax cooler and wondering if there are instances when one should not use it. For example, during times of high humidity, hot weather, cold weather, forest fire smoke in the air, pollen alerts, etc etc...does this make sense? Or can I use it at all times under any conditions.

Btw, does it help vs dew or not at all? Do you guys use them twice a night if you're staying outdoors all night?

Can't wait to get it, I realized enough is enough, as it takes about 2-3 hours for my CPC 1100 to start showing pin point stars, and just when that happens, dew starts creeping up in the middle part of the corrector.

I'd avoid using any active venting in conditions where the scope is cold and the air is warm and wet-- this might lead to the optics dewing up internally, which could end your session before it even begins. This could happen in the summer if you brought out a scope from a cool air conditioned environment to a warm and humid outdoor environment. The opposite can also happen when it's cold outside and warm and moist indoors, so you'd close a cold scope up when you bring it indoors on a chilly night.

Other than that, I don't think there's much reason to avoid using the Lymax.

It won't help to any notable degree in preventing dew formation on the corrector. You'll still need dew prevention-- at the very least, a dew/glare shield. If you want to ensure the longevity of your session, anti-dew heaters are a must for most environments. (folks who live in deserts don't need to worry much about moisture very often!)

If temperatures are dropping quickly over the course of a session, as is normal for most of us, the scope won't be able to keep up. Under those conditions, you'll use the Lymax repeatedly, as soon as thermal issues become limiting/irritating. But, even if you don't swap it in an out throughout the night, it'll still beat waiting 2 hours (or more) for cool-down at the start of the session.

I'd avoid using any active venting in conditions where the scope is cold and the air is warm and wet-- this might lead to the optics dewing up internally, which could end your session before it even begins. This could happen in the summer if you brought out a scope from a cool air conditioned environment to a warm and humid outdoor environment. The opposite can also happen when it's cold outside and warm and moist indoors, so you'd close a cold scope up when you bring it indoors on a chilly night.

Other than that, I don't think there's much reason to avoid using the Lymax.

It won't help to any notable degree in preventing dew formation on the corrector. You'll still need dew prevention-- at the very least, a dew/glare shield. If you want to ensure the longevity of your session, anti-dew heaters are a must for most environments. (folks who live in deserts don't need to worry much about moisture very often!)

If temperatures are dropping quickly over the course of a session, as is normal for most of us, the scope won't be able to keep up. Under those conditions, you'll use the Lymax repeatedly, as soon as thermal issues become limiting/irritating. But, even if you don't swap it in an out throughout the night, it'll still beat waiting 2 hours (or more) for cool-down at the start of the session.

Ok, I see, so if I have it stored in my house during the summer with the air conditioner keeping the temp at about 73-74F (23-24 C) and bring it outside to similar temps but with the humidity over 70? 80? 90%? It's not a great idea.

I should be alright in the winter, I don't use a humidifier.

Trying to figure out what is the maximum humidty % it can be used under.

Yea I use a dew shield and dew heater strap but maybe I haven't been starting it up as soon as I bring the scope out. Would you keep the dew strap running on max all night?

Yea I use a dew shield and dew heater strap but maybe I haven't been starting it up as soon as I bring the scope out. Would you keep the dew strap running on max all night?

I have never run a dew strap at max. I want to run my dew straps at the lowest power setting possible, yet still deliver enough juice to keep it one or two degrees above the dew point. I have always used Kendrick dew straps with a Kendrick controller and I have the outputs programmed at 20, 30, 40, and 50 percent. Depending on the humidity and dew point, I might start out at a higher setting to get the corrector (or meniscus in my case) warm, then I'll dial it down to save the battery. Even at just 30 percent, you will feel the heat if you put your hand on the dew strap.

I also use a Lymax cooler and set it up with the scope about an hour in advance. Virginia is a very humid state, but I have not had any problems with interior dew or other issues. I use a fairly small battery, so the Lymax doesn't blow that hard and mine has a decent filter on the fan.

BTW - My Lymax fan is over ten years old (as is my Kendrick controller) and they both still work great.

I agree with Ron regarding low dew strip settings. I generally start mine off at around 2v or about 16%. If I have to turn them up, transparency has gone down and as such, I have never reached 6v. By then, I've already packed it up. Keep in mind that you only need to raise the temp of the objective/corrector by 1 or 2 degrees above ambient.

I'd avoid using any active venting in conditions where the scope is cold and the air is warm and wet-- this might lead to the optics dewing up internally, which could end your session before it even begins. This could happen in the summer if you brought out a scope from a cool air conditioned environment to a warm and humid outdoor environment. The opposite can also happen when it's cold outside and warm and moist indoors, so you'd close a cold scope up when you bring it indoors on a chilly night.

Other than that, I don't think there's much reason to avoid using the Lymax.

I did this once with my vented C11 with Deep Space Products with Temp-est fans. I wanted to get warm air into the telescope in order to more quickly dissipate the dew that formed on the outside of the corrector when I brought the OTA into a warm house. Ten minutes later, the dew on the corrector had mostly dissipated, but dew had formed on the primary mirror.

It was one of those mistakes that became immediately obvious in hindsight. It didn't do any harm, but forming dew inside the OTA shouldn't be a habit. Having said this, I used the Lymax on my C9.25 often and I liked it. It is a great option for those not wanting to tear open their OTAs to install vents. At least for the C9.25, I find it keeps up with temperature drops on most nights, but it certainly helps to speed up cooling. These days I can set my OTA outside for a couple hours before actually observing/imaging.

There is no reason why a scope needs to reach ambient temperature in order to provide good views. The temperature inside the scope simply needs to be stable. Bringing the temperature of the inside of the scope to the same temperature as the outside of the scope is one way to stabilize the temperature, and tube currents inside the scope. That is what the Lymax is for. The other approach is to insulate the scope so that the temperature inside stays consistent regardless of the temperature outside. This essentially eliminates cool down time instead of reducing it. Reflectix is generally the standard insulating material. You can buy a roll at the hardware store for $10. Add some self adhesive Velcro and get some scissors and make yourself a nice little coat for your Cat. Of course then you want to seal off any tube vents to keep the outside air out, otherwise it defeats the purpose of insulating. For this reason, insulating scopes is primarily used with closed tube scopes, not Newtonians.

I found continuous active venting necessary for getting my 8 and 11" sct's to not display significant thermal issues. Within minutes of turning the fan off, I can watch the "tube seeing" degrade rapidly degrade, as the top of the tube sheds heat to the sky. This isn't typcially a big deal for low to moderate magnifications on DSO's. But, at highest magnifications on planets or difficult doubles, it makes a massive difference.

I haven't tried covering the entire scope with a thermal barrier. But, I have covered the main body, which worked particularly well for me when combined with the fan, and reasonably well for low to moderate mags with the fans off. High mags still needed the fan. Fork mounted scopes, like mine, are somewhat difficult/tedious to insulate thoroughly because of the fork arm and carrier assemblies. My experiments suggested that a very thorough covering of all surfaces... well... not the front ... including the rear casting, would be necessary for me to no longer require active venting, and I just haven't had the moxy to do so. I just turn on the fan instead, mostly because it's already there, and works very well. But, I had to cut my ota, and that was very invasive and dangerous. If I were hesitant to cut the tube, as one should be, I'd go with a thorough thermal barrier application, and observe the results for myself.

I really need to do the thermal barrier thing on my 127mm Mak... I had good results with the tube alone, but never got around to doing the rear casting, as would be necessary...

I found continuous active venting necessary for getting my 8 and 11" sct's to not display significant thermal issues. Within minutes of turning the fan off, I can watch the "tube seeing" degrade rapidly degrade, as the top of the tube sheds heat to the sky. This isn't typcially a big deal for low to moderate magnifications on DSO's. But, at highest magnifications on planets or difficult doubles, it makes a massive difference.

I haven't tried covering the entire scope with a thermal barrier. But, I have covered the main body, which worked particularly well for me when combined with the fan, and reasonably well for low to moderate mags with the fans off. High mags still needed the fan. Fork mounted scopes, like mine, are somewhat difficult/tedious to insulate thoroughly because of the fork arm and carrier assemblies. My experiments suggested that a very thorough covering of all surfaces... well... not the front ... including the rear casting, would be necessary for me to no longer require active venting, and I just haven't had the moxy to do so. I just turn on the fan instead, mostly because it's already there, and works very well. But, I had to cut my ota, and that was very invasive and dangerous. If I were hesitant to cut the tube, as one should be, I'd go with a thorough thermal barrier application, and observe the results for myself.

I really need to do the thermal barrier thing on my 127mm Mak... I had good results with the tube alone, but never got around to doing the rear casting, as would be necessary...

I only insulate the tube, not the rear casing. I agree it is easier for me with the GEM mount. The rear casing is pretty thick and doesn’t lose heat quickly. In your situation you would need to cover the rear casing because of the vent. And you already put a fan in so I agree you might as well use it.

But with insulation, the cool down of the internal optics is slowed down in such a drastic way, that even my plate glass 16" mirror inside my SCT can keep up without the slightest deformations normally caused by temperature differences in the glass!

It means that because of insulation, simple cheap plate (float) glass suddenly is very usable for even the biggest mirrors.

Yes, it took quite some time and tests for me to accept that fact!

Back in 1992, I found my 8" Newtonian not performing well because of thermal issues, in that time we believed that primary's should be quite thick, but that made them a nasty radiator of warmth during the entire night!

I developed a watercool system on my 8" and later on my 12" newt (1995). Cooling that mirror solved the temperature problem completely, yes, the 12" needed some 40 minutes too cool from 21 degrees C towards 5, but I didn't know how much I would gain with a diffraction limited performance of a 12" newt!

Years and years of amazing images would follow, and it still is going strong!

So, in very short:

With optically closed scope's, insulating is the way to go, but of course, that is my own believe based on my experience..

With 'open' systems (newt), insulating is not the way to go, but there a lot is already won by the nowadays much thinner primary mirror.

Point is that the 'inward effect' of any rapid change in temperature outside the telescope, is drasticly slowed down.

It will prevent deformations in the optics, and prevent tube currents.

When you have living conditions with much lower outside temperatures, you can try a little test:

Most new windows have quite decent quality, that makes it possible to have a quite decent image quality when you look through them with a small scope, like a C90 or 80mm refractor.

Point the scope at an object with nice contrasts, observe with the window closed, then open the window, and I think you will be dazzled by the decrease in image quality!!

With the window closed, you somewhat simulate a insulated scope that is warm inside and cold outside.

With the window open, you somewhat simulate an open scope, also warm inside and cold outside, but there the colder outside air is colliding with the warmer inside air, causing turbulence.

There are some who still point at the schmidt corrector plate being the reason insulation would not work, because you cannot insulate that part!

Well, of course, they are a bit right, but glass also still has some insulating capacity, and during all my tests, that insulating capacity still seemed enough prevent the forming of tube currents inside the scope.

My 16 SCT still has absolutely no tube current issues, even after the replacement of the 8mm thick schmidt corrector plate by one that is only 5.7mm thin.

I realize that I'm a bit off topic with this, but I still think that there are members out there who want to know about these relatively new insights.

+1 for yellobeard's comments! It can not be stated enough how valuable his contributions to our hobby(?) have been! My experiences over the last few years, with dozens of SCT and MCT scopes, have mirrored, and verified, his findings. Agree or disagree with him, but at the very least, a debt of gratitude is owed to him for moving the science forward, and teaching us not to automatically "accept" teachings handed down to us for generations.

Indeed you should not use a lymax cooler when the outside air is very moisty!

But in general, it is never a very good idea, to pull (or push) outside air into a closed scope, as you never know what stuff is in the air at that moment, and it is much easier to put nasty stuff inside your scope, than getting it out!

Unless of course you are sure that the air is filltered of dust and low of relative moisture..

Also, a lymax does not have a very high cooling capacity, so apart from the time it already needs to cool the optics, in a situation where the outside temperature signifficantly drops over night, the optics inside will ask for that lymax again when you are further (deeper) in the night.

Hey all, just ordered a Lymax cooler and wondering if there are instances when one should not use it. For example, during times of high humidity, hot weather, cold weather, forest fire smoke in the air, pollen alerts, etc etc...does this make sense? Or can I use it at all times under any conditions.

Btw, does it help vs dew or not at all? Do you guys use them twice a night if you're staying outdoors all night?

Can't wait to get it, I realized enough is enough, as it takes about 2-3 hours for my CPC 1100 to start showing pin point stars, and just when that happens, dew starts creeping up in the middle part of the corrector.